Modélisation des échanges thermiques et de la circulation d'air dans un lit bactérien

La température dans un lit bactérien a une influence prépondérante sur les réactions biologiques qui s'y déroulent.Le modèle développé ici présente une formulation qui permet de calculer un profil de température, et donc une température moyenne de l'eau à l'intérieur du lit bactérien, à partir des grandeurs suivantes : débit et température d'entrée du liquide, température et humidité de l'air extérieur et caractéristiques d'échange thermique de la tour. De plus, il permet d'appréhender la circulation de l'air induite par tirage naturel dans la tour, moyennant la connaissance des coefficients de pertes de charge associés au garnissage utilisé, ainsi qu'aux ouïes d'aération.En sus de la formulation du modèle, les tout premiers résultats d'ajustement du modèle obtenus sur installations pilotes sont présentés. Le développement de la méthode devrait permettre d'optimiser la température de fonctionnement du lit tout en garantissant une circulation suffisante de l'air dans l'appareil.The temperature is one of the main parameters governing the biological reactions in a trickling filter.The present model proposes a set of equations applicable for the determination of a temperature profile, and therefore of an average temperature, inside the trickling filter, when the flowrate and the temperature at entry of the liquid, the ambient air conditions (temperature and humidity) and the thermal exchange coefficients of the tower are known. Moreover, the airflow induced by natural draft is also computed when the head loss coefficients in the media and at entry are known.Beside this formulation, the first results of modal fitting on pilot plants are discussed. With few further developments, the method could be useful for the optimization of the operating temperature in a trickling filter which guarantees a sufficient airflow rate in the tower

Automatisation et comparaison de différentes méthodes respirométriques d'estimation rapide de la DBO

II est bien connu que la DBO peut étre mesurée par des méthodes respiromédriques. Les manipulations sont ainsi rendues plus aisées mais la durée de la mesure reste inchangée. La demande biologique en oxygène à court terme (DBOACT) a été proposée pour évaluer rapidement la DBO. Habituellement, ces mesures étaient réalisées dans un respiromètre fermé avec une boue acclimatée et en état de respiration endogène. Récemment on a suggéré de travailler avec un respiromètre ouvert, aéré continuellement durant le test. Nous avons réalisé un tel appareil avec une acquisition et un traitement automatique des données, en utilisant un micro-ordinateur. De cette façon, il est facile de tester différentes méthodes (intégration de la courbe en sac, hauteur de pic, comparaison à des étalons, usage d'étalons internes) pour évaluer la DBO. Nous avons également examiné l'influence du type de substrat, de l'âge et des caractéristiques des boues. Notre conclusion est que aucune des méthodes testées ne fournit une détermination précise de la DBO5 pour des substrats complexes. La méthode reste utile pour contrôler la variabilité de l'influent dans une station d'épuration, lorsque la biomasse est acclimatée au substrat et qu'on ne désire pas une mesure très précise.The usual way of measuring BOD is the dilution method. The consumption of oxygen is measured in the dark at 20 °C during 5 days. Manometric methods were proposed already some decades ago. Their principle is that every molecule of oxygen consumed la transformed into CO2 which is absorbed in a solution of KOH, creating a pressure variation in the bottle. From this pressure variation the BOD can be calculated. By this way experiments were made easier but the duration of the measure remained unchanged. Other respirometric methods were also proposed, especially Short Term Biological Oxygen Demand (STBOD) to evaluate BOD rapidly. Usually such determinations were done in closed respirometers with acclimated sludge under endogeneous respiration condition. Recently, it was suggested to proceed in an open respirometer aerated continuously during the test. We set up this type of respirometer with acquisition and automatic processing of the data, using a microcomputer. In this way it was easy to test different procedures. Among these procedures we tested :- the method of integration of curve in sack-from,- the method of peak level,- the method of comparison to standards,- the method of internal standards.The principles of these methods are given in more detail in the text. We examined the influence of the type of substrate, of the type of biomass used and of the sludge retention time on the results. The substrates tested were :- glucose,- domestic waste water with and without detergent,- diluted eggs,- diluted beer,- effluents from the paper industry.Three different types of biomass and these sludge retention times (fresh, 5 days and 20 days) were used. Automatisation of the test and automatic processing of the data were carried out in basic language with an « Apple II » microcomputer.The test lasted between 37' and 3 hours 10', depending on the conditions (substrate, concentration, type of sludge,...)Analysis of the results were computerized by the Analysis of Variance (ANO-VA) method and results are lasted in 3 tables.From this study we can conclude that STOD methods have some advantages :- they are much faster than the classical method,- they can be easily automatized,- they are cheap,- oxygen is really consumed by biological processes.For simple substrates these methods can lead to good results but for complex substrates reproductibility and precision are rather poor. Among the methods tested the only acceptable one seems to be the integration of the curve in sack-form. Lack of reproductibility appears to be intrinsic to the method.Some possible improvements are presented, such as washing the activated sludge between two experiments, but are not very practical.Despite these limitations the method can be useful to control the variability of influent in a sewage treatment plant. In such a case, the biomass is acclimated to the substrate and variations of influent BOD can be measured

Potentialités des bioélectrodes et des bioréacteurs à biomasse fixée pour l'estimation rapide de la DBO

La méthode standard de détermination de la Demande Biochimique en Oxygène (DBO-5 jours par dilutions) présente certains inconvénients bien connus dont celui de ne pas être exploitable pour la gestion en temps réel d'un procédé d'épuration. De ce fait, divers types d'appareils d'estimation rapide de la DBO, basés sur des méthodes respirométriques, ont été imaginés dans le passé et même commercialisés pour certains.Dans cette étude, des appareils d'estimation rapide de la DBO de types bioélectrode et réacteurs à biomasse fixée (écoulement piston et parfaitement mélangé) ont été mis en oeuvre, après avoir été développés ou modifiés sur base de concepts déjà existants. Une attention particulière a été portée sur la validité de ces appareils, la crédibilité de leurs mesures et la définition de leur champ d'action.De par leur principe de fonctionnement (injection en flux), la bioélectrode et le bioréacteur piston sont des appareils qui doivent être calibrés et dont la biomasse immobilisée doit être préalablement adaptée à l'échantillon à analyser. La solution de calibration est essentielle et doit être qualitativement la plus proche possible de l'échantillon à analyser.Le bioréacteur parfaitement mélangé se distingue des deux premières méthodes car il travaille théoriquement en consommation totale du substrat. La méthode ne nécessite pas de calibration mais implique, avant toute mesure de respirogramme, la détermination d'un paramètre supplémentaire, le coefficient de transfert de l'oxygène.De manière générale, la principale conclusion de l'étude réside dans la difficulté de ces appareils à fournir une DO (Demande en oxygène) corrélable à la DBO5 conventionnelle. Leur champ d'application reste en effet limité aux substrats rapidement biodégradables.Leurs potentialités restent cependant conformes aux besoins de contrôle rapide des charges organiques polluantes en entrée et sortie des stations d'épuration.BOD (Biochemical Oxygen Demand) is an important parameter to characterize organic pollution in aquatic environments and sewage. The five-day period required by the classical dilution method (BOD5) is incompatible with real-time control of a sewage treatment plant. Moreover, the assay procedure (closed respirometer, very diluted samples) is not only far from real growing conditions but also far from conditions in sewage treatment plants.Several devices for rapid BOD estimation, all based on respirometric methods, have been developed and tested. These devices can be grouped into 2 categories:- an immobilized biomass plug-flow reactor and a bioelectrode, both based on a flow injection principle; - an immobilized biomass perfectly mixed reactor, based on an open respirometer principle. We have focused mainly on validating the principles, checking the measurement reliability, and defining more precisely the scope of the various devices.The bioelectrodeThe BOD bioelectrode that we developed relies on a classical configuration that uses a yeast strain (Trichosporon cutaneum) as the biological receptor and a Clark probe as the transducer. The main changes made in this system are as follows:- a second biomembraneless Clark probe was added to the 16-ml measuring cell to serve as a reference probe in order to remove experimental disturbances (temperature, oxygen transfer coefficient, dissolved oxygen concentration, etc.). - the second change was to include the respirogram area among the data available for processing. The signal utilized in this set-up is the difference between the signals provided by the two probes. Our conclusions are as follows:- Concerning the signal processing, manufacturers are currently guided by the desire to develop devices able to estimate the BOD of a large range of substrates or effluents in a very short time (a few minutes for the newest devices). However, it seems useful, even necessary in many cases (complex mixtures of components that are oxidized at variable rates), to use information provided by the respirogram shape and area. This approach allows one to maximize the BOD bioelectrode's range for a given immobilized strain, although the trade-off is a longer total run time. - Concerning the adaptation period for microorganisms, it is impossible to correctly estimate BOD from various effluents without first adapting the biomaterial to the type of substrate to be analyzed. Therefore it is dangerous to consider a BOD bioelectrode as an analytical instrument, because an adaptation period is required after any change in the composition or, even more so, type of effluent. - Concerning the correspondence between rapid BOD and BOD5, the BOD sensor can detect only the BOD of soluble compounds that can diffuse through the biomembrane and that will be metabolized during the time of analysis. The difference observed between BOD sensor and BOD5 depends on the calibration solution but also and even more on the structure and size of the molecules constituting the sample to be analyzed. - Concerning the choice of calibration solution, choosing the right calibration solution is crucial. The calibration solution should therefore be qualitatively as close as possible to the test sample. The immobilized biomass bioreactorsThe plug-flow reactorThe plug-flow reactor design was validated for simple substrates; its working principle is similar to the bioelectrodes, since it relies on flow-injection analysis (FIA). In the case of the plug-flow reactor, the only usable information for BOD estimation is the respirogram area, as the peak height quickly reaches a rather constant value due to saturation of the immobilized microorganisms. However, the importance of the many physical and biological processes that occur concomitantly in the system (transfer, adsorption, substrate consumption, substrate saturation phenomena, dilution rate, etc.) makes a theoretical mathematical model of the reactor more difficult to establish. A long-term, more fundamental study of various natural or artificial substrates might ultimately enable us to reach such a goal.On the other hand, a variant of this reactor that recirculates the partially-degraded effluent until it is completely consumed yielded a linear correlation between system response (respirogram area) and substrate amount. In this system, oxidation of the rapidly biodegradable substrates is total under our operating conditions. This alternative reactor seems to have some very interesting possibilities, especially with regard to the automation of the system.The perfectly mixed reactorThe utilization of the perfectly mixed reactor for rapid BOD estimation is based on two sequential experiments - although this has the disadvantage of increasing the total run time - to obtain the respirogram area (S) and oxygen transfer coefficient (KL.a), as the units of the product (KL.a x S) of these parameters are equivalent to those of oxygen demand and their product is the variable that best correlates with the substrate injection volume. This correlation was observed for a large range of substrates. In the case of the perfectly mixed reactor, unlike bioelectrodes,- diffusion processes have no effect on measurement, as the substrate is consumed completely during the experiment; - the substrate consumption rate does not affect the measurements, thereby freeing the method from the influence of various experimental parameters (air flow-rate, the quantity of biomass, the liquid volume in the reactor, etc.), as our tests have shown. For a given substrate, the linearity of the correlation between the product of KL.a x S and the amount of substrate is generally excellent. The attempt to correlate the system's response with the BOD5 measurements for a variety of substrates proved to be difficult, however. Although the bioreactor's analytical range is wider than that of bioelectrodes, the system still fails to give any measurable responses for complex substrates such as starch, cellulose, proteins, etc., and the KL.a x S values estimated by the bioreactor remained much lower than the corresponding BOD5 values. KL.a x S is probably characteristic of the portion of the substrate that is degraded rapidly by the microorganisms to meet their immediate energy needs, whereas the remaining substrate is probably kept for reserve and biomass synthesis

Fibronectin Protects from Excessive Liver Fibrosis by Modulating the Availability of and Responsiveness of Stellate Cells to Active TGF-β

Fibrotic tissue in the liver is mainly composed of collagen. Fibronectin, which is also present in fibrotic matrices, is required for collagen matrix assembly in vitro. It also modulates the amount of growth factors and their release from the matrix. We therefore examined the effects of the absence of fibronectin on the development of fibrosis in mice

New constraints on oscillation parameters from Ve appearance and Vu disappearance in the NOvA experiment

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First measurement of neutrino oscillation parameters using neutrinos and antineutrinos by NOvA

The NOvA experiment has seen a 4.4σ signal of ν̄e appearance in a 2 GeV ν̄μ beam at a distance of 810 km. Using 12.33×1020 protons on target delivered to the Fermilab NuMI neutrino beamline, the experiment recorded 27 ν̄μ→ν̄e candidates with a background of 10.3 and 102 ν̄μ→ν̄μ candidates. This new antineutrino data are combined with neutrino data to measure the parameters |Δm322|=2.48-0.06+0.11×10-3 eV2/c4 and sin2θ23 in the ranges from (0.53-0.60) and (0.45-0.48) in the normal neutrino mass hierarchy. The data exclude most values near δCP=π/2 for the inverted mass hierarchy by more than 3σ and favor the normal neutrino mass hierarchy by 1.9σ and θ23 values in the upper octant by 1.6σ

Search for multimessenger signals in NOvA coincident with LIGO/Virgo detections

Using the NOvA neutrino detectors, a broad search has been performed for any signal coincident with 28 gravitational wave events detected by the LIGO/Virgo Collaboration between September 2015 and July 2019. For all of these events, NOvA is sensitive to possible arrival of neutrinos and cosmic rays of GeV and higher energies. For five (seven) events in the NOvA Far (Near) Detector, timely public alerts from the LIGO/Virgo Collaboration allowed recording of MeV-scale events. No signal candidates were found

Search for multimessenger signals in NOvA coincident with LIGO/Virgo detections

Using the NOvA neutrino detectors, a broad search has been performed for any signal coincident with 28 gravitational wave events detected by the LIGO/Virgo Collaboration between September 2015 and July 2019. For all of these events, NOvA is sensitive to possible arrival of neutrinos and cosmic rays of GeV and higher energies. For five (seven) events in the NOvA Far (Near) Detector, timely public alerts from the LIGO/Virgo Collaboration allowed recording of MeV-scale events. No signal candidates were found

Seasonal Variation of Multiple-Muon Cosmic Ray Air Showers Observed in the NOvA Detector on the Surface

We report the rate of cosmic ray air showers with multiplicities exceeding 15 muon tracks recorded in the NOvA Far Detector between May 2016 and May 2018. The detector is located on the surface under an overburden of 3.6 meters water equivalent. We observe a seasonal dependence in the rate of multiple-muon showers, which varies in magnitude with multiplicity and zenith angle. During this period, the effective atmospheric temperature and surface pressure ranged between 210 K to 230 K and 940mbar to 990mbar, respectively; the shower rates are anti-correlated with the variation in the effective temperature. The variations are about 30% larger for the highest multiplicities than the lowest multiplicities and 20% larger for showers near the horizon than vertical showers